The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In packet switching networks a packet flow or traffic flow is a sequence of packets between two or more internetworking elements or network nodes such as routers, switches, or computer systems. Improving network performance visibility by collecting metrics related to traffic flows is important to both service providers and customers to manage the network and monitor application performance. For example, service providers may need to determine if there is network degradation or congestion at a particular network node. As another example, customers may need to know, if there is Quality of Service (“QoS”) throttling or queuing at a particular network node or may require metrics regarding an application's performance in order to quickly detect potential problems before they have a significant impact.
One approach involves measuring jitter. For any pair of consecutive network packets, jitter is the mean deviation of the difference in packet spacing at a receiving network node compared to the spacing at a corresponding sending network node. For example, for real time transport protocol (“RTP”), if a sending network node sent packet i at the time Si, and a receiving network node received the packet at time Ri, then the jitter value is calculated as:Ji=|(Ri+1−Ri)−(Si+1−Si)|Currently RTP jitter is supported in most internetworking nodes according to Request for Comments (“RFC”) 3550 of the Internet Engineering Task Force. Collecting RTP jitter metric data contributes to network overhead because it requires every network packet to be time stamped and requires including the time stamps in the RTP header by the sending network node.
Similarly, another approach is to measure the jitter for packets sent using the User Datagram Protocol (“UDP”). UDP jitter is supported by certain commercial products of Cisco Systems, Inc., San Jose, Calif. UDP jitter metric requires sending active probe packets to obtain the measurements and requires software, typically at a management station, to initiate sending the packets and to receive and interpret responses.
The existing methods of collecting metrics relating to packet flow are inadequate as they involve significant overhead, can only be implemented for certain network protocols, are difficult to deploy, and place a burden on the network nodes that forward the traffic.